One of the important offerings of an interactive cable TV ("ITV") system is providing customers with the opportunity for ordering movies for viewing on their cable-attached televisions. There are two methods of delivering these movies. One is called Video on Demand ("VOD"), where the customer selects a title from a number of movies using a menu on the TV screen, and the movie is presented for immediate viewing. In a variation of the VOD case, a few movies are offered at specific times. This is called Near Video on Demand ("NVOD"). In both cases, the movies must be stored by the cable companies in such a way that customers have access to them. Today, a likely way of providing movies for customer viewing is to digitize them and store them on a form of computer called a video server.
Given the hierarchical nature of a cable system, there are numerous locations that could be used for storing movies. FIG. 1 illustrates the structure of a typical cable TV system. Neighborhoods (cells) are serviced by hubs and the hubs are connected to a headend. Headends could be interconnected and connected upstream to more centralized asset providers (not shown) containing video servers.
FIG. 2 illustrates a generalized system with n levels of interconnectivity. Movies for customer access could be stored in the hubs, the point closest to the customer. This theoretically would have the lowest connectivity costs, but movies of interest would have to be replicated at each hub. Connectivity costs include:
Network equipment PA1 Costs associated with the physical connection PA1 Bandwidth and network usage
Switches PA2 Gateways PA2 Concentrators PA2 Routers PA2 Bridges PA2 Adapters PA2 etc. PA2 Wire PA2 Fiber optics PA2 Repeaters PA2 Transformers PA2 Receivers PA2 Satellite dishes PA2 etc. PA2 Tariffs PA2 Access charges PA2 Management overhead PA2 etc.
An option would be to store movies at the next highest group of nodes in the distribution tree. Connectivity costs would probably be more than for hub connectivity, but the movies would be replicated fewer times. This pattern continues as one moves up the cable system hierarchy towards the headend--higher connectivity costs and lower storage costs.
A cable company operator needs to determine the best way to distribute movie storage to minimize the overall system costs. Assuming connectivity costs are only incurred during movie viewing and connectivity costs rise as the distance from server to user increases, it is practical to assume that the most popular movies should be placed nearest to the customer at the hub. Less popular movies should be stored at higher nodes in the system. The problem becomes one of trading connectivity costs for storage costs, and then determining at what point the minimum overall cost occurs. The prior art has examined this problem by proposing complex models based on network traffic, viewer patterns, and other parameters. This invention proposes a more simple model based on movie popularity, storage costs, and connectivity costs.